tuna: fix mount USB storage (OTG support)

It solves error in DirectVolume:
Vold managed volumes must have auto mount point; ignoring /storage/usbdisk

PS2: Solves:
/dev/block/vold/8:1 failed to mount via VFAT (No such file or directory)
Volume usbdisk found no suitable devices for mounting :(

Now, it's working fine

Change-Id: I7dd061c0e0cfb068b88cf8b6ce210a98c5ffe176